The invention claimed and disclosed herein pertains to multi-color imaging apparatus, and more particularly to methods and apparatus for reducing wear on selected toner distribution components within a multi-color imaging apparatus.
Multi-color imaging apparatus are well known in the art. Such imaging apparatus can include printers, photocopiers, and multi-function imaging apparatus. Multi-function imaging apparatus typically include the capability to function as a printer and a photocopier, and can include other capability as well, such as performing the functions of a facsimile machine. By xe2x80x9cmulti-colorxe2x80x9d we mean that the imaging apparatus can produce an image having two or more colors, which can include black as a color. Typically, multi-color imaging apparatus are four-color imaging apparatus, which use four base imaging substances (ink or toner) of yellow, magenta, cyan and black to allow a palette of a large number of colors to be imaged. This is typically accomplished by imposing the base colors on top of one another, or in close proximity to one another, and can be enhanced by varying the density of the applied base colors relative to one another. Multi-color imaging apparatus can take the form of liquid ink-jet printing devices, as well as electrophotographic imaging apparatus. The present invention is particularly directed to the latter type of color imaging apparatus.
The electrophotographic (xe2x80x9cEPxe2x80x9d) imaging process is well understood in the art, and need not be described further herein. However, to provide a basis for the following discussion, we will now provide a very brief overview of the EP imaging process. For EP imaging, a light-sensitive optical photoconductor (xe2x80x9cOPCxe2x80x9d) is provided, which is initially provide with a base charge (either positive or negative). The OPC is then selectively exposed by an exposing device (commonly a scanned laser, but light emitting diodes (xe2x80x9cLEDsxe2x80x9d) can also be used) to produce at least a portion of an image on the OPC. The selectively exposed OPC is then placed in contact with an imaging substance (here, toner) having a static electrical potential. The toner is then attracted to (or repelled from) the selectively exposed portions of the OPC, such that a portion of the image to be reproduced is placed on the OPC by the toner. The toner on the OPC is then transferred (directly or indirectly) from the OPC to a sheet of imaging media. The imaging media can be a sheet of paper, a transparency, card stock, or other such media. The transfer of the toner from the OPC to the imaging media is typically accomplished using a corona discharge unit or a charged roller which attracts toner away from the OPC and onto the imaging media. The toner on the imaging media is then fixed to the imaging media using a fusing station, which can use heat and/or pressure to fuse the transferred toner to the imaging media.
The imaging substance (toner) used in the EP imaging process is typically provided in a replaceable cartridge (a xe2x80x9ctoner cartridgexe2x80x9d), which can be replaced when the cartridge is depleted of toner or is otherwise deemed to be beyond the useful life of the cartridge (as will be discussed further below). For typical four-color EP imaging, four toner cartridges are provided: a cartridge containing black toner, a cartridge containing yellow toner, a cartridge containing cyan toner, and a cartridge containing magenta toner. Black toner is typically comprised of carbon particles which can be statically electrically charged, and thus black toner is commonly known as a xe2x80x9cmagneticxe2x80x9d toner. The electro-static properties of black toner allow it to be easily transferred from place-to-place by electrostatic processes. However, toners for the colors yellow, cyan and magenta are typically comprised of plastic or polymeric particles which do not have the electrostatic properties that black toner has. Accordingly, these non-black toners are typically mixed with a transfer agent that has electrostatic properties and attaches to the polymeric color particles, thus facilitating electrostatic transfer of these polymeric particles in the EP imaging process.
For multi-color EP imaging, a number of different configurations are known. They include at least the following:
I) An imaging apparatus configured to receive two or more (typically four) toner cartridges and two or more (typically four) separate OPC cartridges. (See for example U.S. Pat. No. 5,615,002, which is hereby incorporated herein by reference in its entirety). In this configuration, each OPC cartridge is associated with a respective toner cartridge. The OPC cartridges transfer toner from the respective toner cartridges to an intermediate transfer device (either a belt or a drum). The various colors from the toner cartridges are built-up on the intermediate transfer device (xe2x80x9cITDxe2x80x9d) to form an image, and the accumulated toner on the ITD is then transferred to a sheet of imaging media to form the final image. This process is commonly known as a xe2x80x9cfour-passxe2x80x9d imaging process, since the ITD must pass the four OPCs four times to allow all four colors to be accumulated on the ITD. This process allows a wide range of imaging colors since the four colors can be applied on top of one another in various combinations to create a wide range of colors.
II) An imaging apparatus as described immediately above, but wherein the OPCs are incorporated into the toner cartridges. That is, rather than having separate OPC cartridges, the OPCs are part of the respective toner cartridges.
III) An imaging apparatus configured to receive two or more (typically four) toner cartridges, and having a single resident OPC. This configuration provides a low cost multi-color imaging solution. In this configuration, the single resident OPC can be a drum or a belt which can be singly or multiply exposed to form an image thereon. However, due to the difficulty of exposing an OPC through previously developed areas of the OPC (i.e., areas where toner has already been applied to the OPC), in this application the OPC is typically charged only a single time, and then is selectively discharged and selectively exposed to for the four colors. That is, this arrangement typically does not allow for color-on-color toner application to the OPC, but provides for color-next-to-color toner application to the OPC. This arrangement can be described as xe2x80x9csingle-passxe2x80x9d (versus xe2x80x9cfour-passxe2x80x9d) color imaging, and allows for a much faster imaging time, but at the cost of a limited palette of colors, and reduced quality of the resulting image.
IV) An imaging apparatus having a rotating carousel configured to receive a plurality (typically four) toner cartridges (each cartridge having a dedicated OPC), and an intermediate transfer device (ITD). The toners of various colors are built-up on the ITD device individually. A first toner cartridge is placed in proximity to the ITD, and after the first toner has been applied to the ITD, the carousel rotates to allow the second toner cartridge to place toner on the ITD. Once all of the toner cartridges have been allowed to place toner on the ITD, and thus build-up the image on the ITD, the resultant image is then transferred from the ITD to a sheet of imaging media.
In each of these configurations there are a number of rotating cylindrical toner transfer devices. These toner transfer devices can include at least the following devices: the OPC; a toner transfer roller to transfer toner from a toner reservoir to the OPC; a charge roller which is used to charge the OPC with a base charge; and a cleaning brush. In some configurations a corona discharge unit is used instead of a charge roller OPC to charge the OPC. Further, the OPC typically is in contact with a cleaning blade which scrapes any residual toner from the OPC before the OPC is recharged. In some applications a doctor blade is in contact with the toner transfer roller to more evenly distribute toner across the transfer roller before the toner is transferred to the OPC. Each time one of these rotating toner transfer devices is cycled (rotated) it experiences a small amount of wear. Over time, these rotating toner transfer devices should be periodically replaced to maintain image quality and also to avoid mechanical failure. To this end, many EP imaging apparatus are provided with counters or sensors which count or detect the number of cycles a rotating toner transfer device has experienced. When the recommended life of the device expires, the imaging apparatus can signal a user via a user display that it is time to replace the device. In other configurations, to reduce the chance of damage to an imaging apparatus, the imaging apparatus can be configured to disable operation of the imaging apparatus until the recommended replacement is made.
In addition to the toner transfer devices mentioned above, there can be other components (such as gears and belts) that drive the rotating toner transfer devices. These components also experience wear as they are cycled during operation.
The counters that are used to record the number of rotations of a rotating toner transfer device can take a number of different configurations. In one configuration the counter can be software driven. In this example a xe2x80x9cuseful lifexe2x80x9d value is automatically stored in a computer readable memory when a new rotating toner transfer device is placed into the imaging apparatus, and each time an image is generated the xe2x80x9cuseful lifexe2x80x9d value is decreased by a given amount. When the xe2x80x9cuseful lifexe2x80x9d value reaches a preselected number (zero, for example) then the imaging apparatus can notify the user that the respective device has reached the end of its recommended life. In another configuration, a sensor can be placed next to the rotating toner transfer device. Each time the device is rotated the sensor detects the number of rotations, and the detection signal is accumulated in a memory device. When the accumulated value in the memory devices reaches a value equivalent to xe2x80x9cuseful lifexe2x80x9d, the user can be notified.
In at least the first three of the four configurations of multi-color imaging apparatus described above, all of the rotating toner transfer devices in the imaging apparatus are cycled each time an image is generated. Thus, for example, if a user is printing a black-and-white text document using a four-color imaging apparatus, the OPCs for all four toners (black (B), yellow (Y), cyan (C) and magenta (M)) will be cycled. Since only the OPC for black toner is being used, this results in needless cycling of, and wear on, the yellow, cyan and magenta OPCs. Further, if the OPC is located within a toner cartridge, the imaging apparatus can indicate to a user that the cartridge needs to be replaced based on wear of the OPC even when there may still be a useful quantity of toner remaining in the cartridge. For many multi-color imaging apparatus the number of black-and-white images generated is a significant fraction of the overall number of images generated. Accordingly, the non-black toner transfer devices in these multi-color imaging apparatus experience a significant amount of unnecessary wear.
One embodiment of the present invention is a multi-color imaging apparatus configured to support a plurality of color-associated rotatable-toner-transfer-devices. The imaging apparatus includes a rotatable-toner-transfer-device disengagement unit configured to selectively disengage a selected color-associated rotatable-toner-transfer-device. The selection is dependent on whether the selected color-associated rotatable-toner-transfer-device is required to generate an image. In one non-limiting example the imaging apparatus can further include a processor and a computer readable memory device. In this example a rotatable-toner-transfer-device disengage program can be stored in the memory device. The program is executable by the processor to allow the rotatable-toner-transfer-device disengagement unit to selectively disengage the selected color-associated rotatable-toner-transfer-device.
Another embodiment of the present invention is a method of reducing wear on wearable color-associated components within a multi-color imaging apparatus configured to generate both single-color and multi-color images on imaging media. The method includes identifying a selected color-associated component which will not be used to generate the image, and disengaging the selected color-associated component during imaging of the image. Non-limiting examples of wearable color-associated components within the multi-color imaging apparatus include an optical photoconductor and a toner distribution roller.
These and other aspects and embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein: